Engineering pKa value of 3° amine for enhanced production of dialkyl carbonate via Se-catalyzed oxidative carbonylation

Abstract

C1 chemistry plays a vital role in the chemical and energy industry in terms of recycling C1 molecules and high productivity. As one of the C1 chemistry reactions, oxidative carbonylation of alcohols to corresponding dialkyl carbonates (DACs) has been studied but still has problems with catalysts in terms of corrosion and low yield of DACs. To address this issue, various Se/Ph2Se2/tertiary amine catalytic systems were applied to the oxidative carbonylation of alcohols to produce DACs, and Se/Ph2Se2/DMAP showed higher catalytic activity [60.9% yield of bis(2-methoxyethyl) carbonate (BMEC) at a turnover frequency (TOF) value = 32.5 h−1] compared to other tertiary amines (TAs) systems in the oxidative carbonylation of 2-methoxyethanol (MEG). Moreover, with this catalytic system, the oxidative carbonylation of C1–C4 n-alcohols yielded over 40% of DACs with high TOF value (over 40 h−1), which are unprecedented catalytic activity in terms of both yield and TOF value, compared with previous reports. We also found a relationship between the hydrogen bond (HB) strength of alcohol···TA and the catalytic performances. Additionally, the catalytic activity with pKa of TA showed volcano-type correlation. Finally, we investigated the role of TA and proposed a plausible mechanism based on 1H NMR study and the aforementioned correlations.